1. Field of the Invention
The present invention relates generally to the external fixation of bones. More particularly, the present invention relates to an angular correction module for an external fixator which facilitates the gradual angular correction of bone deformities and malunions. More specifically, but without restriction to the particular embodiment and/or use which is shown and described for purposes of illustration, the present invention relates to a method and apparatus incorporating a module for articulating a first bone screw clamping assembly relative to a second bone screw clamping assembly about a center of rotation spaced from the module.
2. Discussion of the Related Art
In various orthopedic surgical procedures, it is necessary to secure two bone portions in a relatively fixed relationship to each other. For example, the need for establishing such a secured relationship is often a result of a fracture which has occurred to the bone. To ensure that the bone can regenerate in the proper orientation and fuse the fracture, it is important that the bone portions be fixed in the desired position during bone regeneration.
Various external fixation devices for the repair of traumatized bone are known. For example, U.S. Pat. No. 5,662,650 to Bailey et al. discloses an apparatus for the external fixation of large bones. The apparatus is illustrated to include a main body as well as a first and second bone screw clamps. The main body serves to allow the apparatus to axially rotate, thereby providing a proper longitudinal rotational location of the bone screws with respect to a bone. The first bone screw clamp is used to secure a first bone screw to the apparatus while permitting the first bone screw to be axially displaced from the main body. In a similar fashion, the second bone screw clamp functions to secure a second bone screw to the apparatus and to allow the second bone screw to be axially displaced with respect to the main body. U.S. Pat. No. 5,662,650 is incorporated by reference as if fully set forth herein.
In certain orthopedic surgical procedures, it is necessary to engage two bone portions in a fixed relationship and angularly adjust the two bone portions relative to each other. The need for making such an adjustment is frequently the result of bone deformity. Such bone deformities may result from congenital defects including but not limited to Blount's Disease, Tibia Vara, Paget's Disease and Hypophosphatemic Rickets. Angular adjustment of bone portions may also be required as a result of post-traumatic applications, such as the correction of bone malunions.
Other known devices are available for the correction of bone deformities and malunions. For example, the various products manufactured by Orthofix S.r.l. include a fixator having an elongated main body pivotally attached to a T-clamp. The T-clamp attaches to a plurality of bone pins. This fixator further includes a removable compression-distraction unit for angular correction of a bone. The compression-distraction unit attaches to the main body and the T-clamp. Through compression and distraction the unit functions to pivot the T-clamp relative to the main body, and thereby angularly correct the bone.
While the fixators specifically for correcting bone deformities and malunions of the type described above may have proven acceptable for certain applications, such fixators are nevertheless susceptible to improvements that may enhance their performance of the fixator. In this regard, known devices for external bone fixation are typically not suitable for articulating a first bone screw clamping assembly relative to a second bone screw clamping assembly about a center of rotation passing through an axis of the bone.